keep in mind that these videos are made by community members and aren’t updated regularly,
consider using these instructions as guidelines and the written tutorial here as reference
Video tutorial on how to install GTA5 Redux v1.2 (Outdated)
(Don’t replace the gameconfig.xml described in the video, it is not necessary with Redux 1.2.1)
Big thanks to cupofacid for making this video.
Video tutorial on how to install GTA5 Redux v1.1 (Outdated)
Big thanks to WhatComesAround for making this video.